1. Field of the Invention
The present invention is directed to capacitors and relates more particularly to a monolithic multi-layer ceramic capacitor (MLC).
Electronic devices such as computers, television sets, radio transmitting and receiving equipment, and micro-chip controlled circuits utilize a multiplicity of MLCs. MLCs are frequently employed in the power supply circuits associated with intergrated circuit devices as a means of damping pulses associated with the operation of such devices. MLCs typically comprise a multiplicity of thin layers of ceramic dielectric material with interposed layers of electrode material.
While mass production technics and testing procedures of fabricated MLCs have been devised which minimize the possibility of short circuiting between adjacent layers of electrodes in MLCs, it is not an uncommon experience to find an MLC which is shorted either by virtue of mishandling in application, or by incipient weaknesses in the ceramic layer resulting in shorts after periods of use of the electronic device. When a capacitor short circuits, the resultant uncontrolled electrical flow often causes damage to associated components in the electronic device such that the failure of a capacitor, which is relatively inexpensive, may induce significant and expensive damage to associated components. THE PRIOR ART
Various means have been suggested to eliminate or minimize the damages which may flow from ceramic capacitor failures. By way of example, it has been proposed to provide a fuse combined with a monolithic ceramic capacitor (U.S. Pat. Nos. 4,107,759 and 4,193,106). Other examples of fuses embodied in or combined with capacitors of various sorts may be found in the following U.S. Patents:
______________________________________ 2216558 3579062 2216559 3638083 2704341 4107762 3236976 4150419 3249835 4186417 3579061 4442473 ______________________________________
An alternative approach to the fused capacitor design has been to embody fusing in the printed circuit devices to which the capacitor is attached. Representative examples of prior art patents adopting such approach are:
______________________________________ 3500276 4072976 3699395 4342977 4042950 4394639 ______________________________________
While the provision of fusing mechanisms as represented by the prior art patents cited above have been relatively effective in protecting equipment associated with the failed capacitor, the diagnosing of such failure and the replacement of the failed capacitor and fuse result in significant down time of the electronic device and the expenditure of significant technician time in effecting repair.